Waterproof member and electronic device

ABSTRACT

The waterproof member of the present disclosure is a waterproof member comprising a waterproof membrane configured to prevent entry of water while permitting sound and/or gas to pass therethrough, and a support layer having air permeability in a thickness direction thereof, wherein the member has a joining region where the waterproof membrane and the support layer are joined, and a non-joining region where the waterproof membrane and the support layer are spaced apart from each other, the non-joining region is surrounded by the joining region when viewed in a direction perpendicular to a main surface of the waterproof membrane, and a thickness of the support layer in the non-joining region is less than 100 μm. The waterproof member of the present disclosure is, for example, a waterproof sound-transmitting member including a waterproof sound-transmitting membrane and a support layer for the membrane and having improved sound transmission characteristics.

TECHNICAL FIELD

The present invention relates to a waterproof member and an electronicdevice.

BACKGROUND ART

Electronic devices such as mobile phones, smartphones, wearable devicesincluding smart watches, and cameras have an audio function. A soundconverter (transducer) such as a speaker and a microphone is housedinside a housing of an electronic device having an audio function. Thehousing of the electronic device is provided with an opening (externalsound-transmitting port) for introducing sound from the outside to thesound converter and/or from the sound converter to the outside. Entry ofwater into the housing has to be prevented. Thus, a waterproofsound-transmitting membrane that prevents entry of water whilepermitting sound to pass therethrough is attached to the externalsound-transmitting port.

A waterproof sound-transmitting member that includes a waterproofsound-transmitting membrane and a support layer supporting the membranehas been known. Since the support layer is included in the member, forexample, breaking of the waterproof sound-transmitting membrane due tothe water pressure applied to the member when an electronic device isdropped into water can be prevented. Patent Literature 1 discloses awaterproof sound-transmitting member in which a porouspolytetrafluoroethylene (hereinafter, referred to as “PTFE”) membraneand a porous support layer are selectively bonded to each other atperipheral portions thereof.

CITATION LIST Patent Literature

Patent Literature 1: JP 2002-502561 A

SUMMARY OF INVENTION Technical Problem

In the waterproof sound-transmitting member of Patent Literature 1, thewaterproof sound-transmitting membrane and the support layerindependently freely vibrate in the inner non-bonding region where thewaterproof sound-transmitting membrane and the support layer are notbonded to each other, whereby high sound transmission characteristicscan be obtained even through the support layer is included. However, inorder to respond to size reduction of electronic devices, the size ofthe waterproof sound-transmitting member also tends to be limited.Therefore, further improvement of sound transmission characteristics isrequired for the waterproof sound-transmitting member.

Moreover, a waterproof membrane may be attached to an opening that isprovided in a housing of an electronic device and through whichtransmission of sound is not required. The opening is, for example, aventilation port for ensuring ventilation between the inside and theoutside of the housing. In this case, the waterproof membrane servesonly as a waterproof air-permeable membrane that prevents entry of waterwhile permitting gas to pass therethrough. A waterproof air-permeablemember that includes a waterproof air-permeable membrane and a supportlayer supporting the membrane is also used.

It is an object of the present invention to improve the characteristicsof a waterproof member that is a waterproof sound-transmitting memberand/or a waterproof air-permeable member.

Solution to Problem

Conventionally, improvement of the sound transmission characteristics ofa waterproof sound-transmitting member that includes a waterproofsound-transmitting membrane and a support layer is achieved byimprovement of the sound transmission characteristics of the waterproofsound-transmitting membrane. However, there is a limit to improvement ofthe sound transmission characteristics only by improvement of thewaterproof sound-transmitting membrane. In addition, the improvement ofthe sound transmission characteristics of the waterproofsound-transmitting membrane may reduce the waterproofness of thismembrane. Through the study by the present inventors, it has been foundthat, in a waterproof sound-transmitting member formed by selectivelybonding a waterproof sound-transmitting membrane and a support layer toeach other, improvement of the support layer improves the soundtransmission characteristics. This improvement of the support layer canalso improve the characteristics of the waterproof air-permeable member.

Specifically, the present invention provides a waterproof memberincluding a waterproof membrane configured to prevent entry of waterwhile permitting sound and/or gas to pass therethrough, and a supportlayer having air permeability in a thickness direction thereof, wherein

the member has

-   -   a joining region where the waterproof membrane and the support        layer are joined, and    -   a non-joining region where the waterproof membrane and the        support layer are spaced apart from each other,

the non-joining region is surrounded by the joining region when viewedin a direction perpendicular to a main surface of the waterproofmembrane, and

a thickness of the support layer in the non-joining region is less than100 μm.

According to another aspect, the present invention provides anelectronic device including:

a housing having an opening; and

the waterproof member of the present invention attached to the housingso as to close the opening, wherein

the member is attached to the housing such that the waterproof membraneside of the member faces the outside of the housing and the supportlayer side of the member faces the inside of the housing.

Advantageous Effects of Invention

According to the present invention, the characteristics of a waterproofmember including a waterproof membrane and a support layer for themembrane can be improved, including improvement of the soundtransmission characteristics of a waterproof sound-transmitting memberincluding a waterproof sound-transmitting membrane and a support layerfor the membrane.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a cross-sectional view schematically showing an example ofthe waterproof member (waterproof sound-transmitting member) of thepresent invention.

FIG. 1B is a plan view of the waterproof sound-transmitting member shownin FIG. 1A as seen from the waterproof sound-transmitting membrane side.

FIG. 2 is a cross-sectional view schematically showing another exampleof the waterproof member (waterproof sound-transmitting member) of thepresent invention.

FIG. 3 is a cross-sectional view showing still another example of thewaterproof member (waterproof sound-transmitting member) of the presentinvention.

FIG. 4 is a cross-sectional view showing still another example of thewaterproof member (waterproof sound-transmitting member) of the presentinvention.

FIG. 5 is a cross-sectional view showing still another example of thewaterproof member (waterproof sound-transmitting member) of the presentinvention.

FIG. 6 is a cross-sectional view showing still another example of thewaterproof member (waterproof sound-transmitting member) of the presentinvention.

FIG. 7 is a front view showing an example of an electronic device(smartphone) in which the waterproof member (waterproofsound-transmitting member) of the present invention is attached to anopening (external sound-transmitting port) of a housing.

FIG. 8 is a diagram for describing an evaluation method for the soundtransmission characteristics of a waterproof sound-transmitting member,conducted in Examples.

DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments of the present invention will be described withreference to the drawings. The present invention is not limited to theembodiments described below.

FIG. 1A and FIG. 1B show an example of the waterproof sound-transmittingmember of the present invention. FIG. 1B shows a waterproofsound-transmitting member 1 as seen from the waterproofsound-transmitting membrane 2 side. FIG. 1A shows a cross-section A-Ashown in FIG. 1B.

The waterproof sound-transmitting member 1 has a joining region 5 wherea waterproof sound-transmitting membrane 2 and a support layer 3 arejoined, and a non-joining region 4 surrounded by the joining region 5when viewed in a direction perpendicular to a main surface of thewaterproof sound-transmitting membrane 2 (FIG. 1B). The joining region 5includes regions of peripheral portions of the waterproofsound-transmitting membrane 2 and the support layer 3. The waterproofsound-transmitting membrane 2 and the support layer 3 are joined by ajoining portion 6.

As shown in FIG. 1A, in the non-joining region 4, the support layer 3 isspaced apart from the waterproof sound-transmitting membrane 2. Thesupport layer 3 has air permeability in the thickness direction thereof.The thickness of the support layer 3 in the non-joining region 4 is lessthan 100 μm. That is, in the non-joining region 4, the support layer 3having air permeability in the thickness direction thereof and having athickness less than 100 μm is placed so as to be spaced apart from thewaterproof sound-transmitting membrane 2.

The waterproof sound-transmitting member 1 can be attached to a housingof an electronic device having an audio function. The waterproofsound-transmitting member 1 can be attached to the housing such that thewaterproof sound-transmitting member 1 covers an externalsound-transmitting port and such that the waterproof sound-transmittingmembrane 2 side of the waterproof sound-transmitting member 1 faces theoutside (external space). The waterproof sound-transmitting member 1including the waterproof sound-transmitting membrane 2 can prevent entryof water into the electronic device through the externalsound-transmitting port while allowing transmission of sound between theoutside and a sound converter included in the electronic device.Moreover, when water pressure is applied to the externalsound-transmitting port of the electronic device to which the waterproofsound-transmitting member 1 is attached, the waterproofsound-transmitting membrane 2 becomes deformed in the direction to thesupport layer 3 (the direction from the outside to the inside of thehousing) in the non-joining region 4. However, in the waterproofsound-transmitting member 1, the deformation of the waterproofsound-transmitting membrane 2 is limited in a certain range by contactbetween the deformed waterproof sound-transmitting membrane 2 and thesupport layer 3, so that breaking of the waterproof sound-transmittingmembrane 2 is prevented. Therefore, since the waterproofsound-transmitting member 1 includes the support layer 3, the waterproofsound-transmitting member 1 can have waterproofness (for example, limitwater entry pressure) higher than the waterproofness of the waterproofsound-transmitting membrane 2.

The deformation that remains in the waterproof sound-transmittingmembrane 2 even after being released from the water pressure(hereinafter, referred to as “permanent deformation”) decreases thesound transmission characteristics of the waterproof sound-transmittingmember 1. The support layer 3 can reduce the permanent deformation ofthe waterproof sound-transmitting membrane 2 by limiting deformation ofthe waterproof sound-transmitting membrane 2.

The shapes of the waterproof sound-transmitting member 1 and thenon-joining region 4 are not limited. In the example shown in FIG. 1Aand FIG. 1B, the waterproof sound-transmitting member 1 is rectangular,and the non-joining region 4 is circular, when viewed in the directionperpendicular to the main surface of the waterproof sound-transmittingmembrane 2. The shapes of the waterproof sound-transmitting member 1 andthe non-joining region 4 are, independently of each other, for example,a circle (including a substantially circular shape), an ellipse(including a substantially elliptical shape), and a polygon including arectangle and a square. The corners of the polygon may be rounded. Thewaterproof sound-transmitting member 1 can be attached, for example,between a sound-transmitting port (internal sound-transmitting port) ofthe sound converter and a sound-transmitting port (externalsound-transmitting port) provided in the housing such that the surfaceof the waterproof sound-transmitting member 1 at the support layer 3side covers the internal sound-transmitting port and the surface of thewaterproof sound-transmitting member 1 at the waterproofsound-transmitting membrane 2 side covers the externalsound-transmitting port.

The shape of the joining region 5 is not limited as long as the shape isa shape surrounding the non-joining region 4. The joining region 5 istypically a region including the peripheral portion of the waterproofsound-transmitting membrane 2 and/or the support layer 3. In the exampleshown in FIG. 1A and FIG. 1B, the region other than the joining region 5where the waterproof sound-transmitting membrane 2 and the support layer3 are joined is the non-joining region 4. In the example shown in FIG.1A and FIG. 1B, in the non-joining region 4, the waterproofsound-transmitting membrane 2 is exposed on one surface of thewaterproof sound-transmitting member 1. In addition, in the non-joiningregion 4, the support layer 3 is exposed on the other surface of thewaterproof sound-transmitting member 1.

The waterproof sound-transmitting member 1 can have high soundtransmission characteristics even though the waterproofsound-transmitting member 1 has the non-joining region 4 having areduced area. The area of the non-joining region 4 when viewed in thedirection perpendicular to the main surface of the waterproofsound-transmitting membrane 2 is, for example, 12 mm² or less. The areaof the non-joining region 4 may be 10 mm² or less, 8.0 mm² or less, 5.0mm² or less, 3.2 mm² or less, 2.0 mm² or less, or even 1.8 mm² or less.The lower limit of the area of the non-joining region 4 is not limited,and is, for example, 0.02 mm² or more. The waterproof sound-transmittingmember 1 is suitable for use in a small-size electronic device having anaudio function. An example of the small-size electronic device is awearable device such as a smart watch.

Regarding the waterproof sound-transmitting member 1, the proportion ofthe area of the non-joining region 4 to the sum of the area of thejoining region 5 and the area of the non-joining region 4 when viewed inthe direction perpendicular to the main surface of the waterproofsound-transmitting membrane 2 is not limited, and is, for example, 1 to90%. The upper limit of the proportion may be 50% or less, 20% or less,15% or less, or even 10% or less. As the proportion decreases, that is,as the proportion of the joining region 5 in the waterproofsound-transmitting member 1 increases, the waterproof sound-transmittingmembrane 2 and the support layer 3 can be more firmly joined. Thus, asthe proportion decreases, the degree of deformation and permanentdeformation of the waterproof sound-transmitting membrane 2 due to waterpressure can be reduced more, so that the waterproofness of thewaterproof sound-transmitting member 1 can be increased further, and adecrease in the sound transmission characteristics of the waterproofsound-transmitting member 1 due to water pressure can be inhibited morereliably.

The shape of the waterproof sound-transmitting membrane 2 and the shapeof the support layer 3 may be the same or different from each other,when viewed in the direction perpendicular to the main surface of thewaterproof sound-transmitting membrane 2. In the example shown in FIG.1A and FIG. 1B, the shape of the waterproof sound-transmitting membrane2 and the shape of the support layer 3 are the same and are also thesame as that of the waterproof sound-transmitting member 1.

The thickness of the waterproof sound-transmitting member 1 is, forexample, 500 μm or less. The thickness of the waterproofsound-transmitting member 1 may be 300 μm or less, 250 μm or less, oreven 200 μm or less. The lower limit of the thickness of the waterproofsound-transmitting member 1 is not limited, and is, for example, 60 μmor more. The waterproof sound-transmitting member 1 is suitable for usein a small-size electronic device for which the volume of the interiorof a housing is limited. In addition, in an electronic device having anaudio function, as the distance from an external sound-transmitting portto a sound converter increases, sound resulting from conversion by thesound converter tends to be deteriorated. The deterioration of the soundbecomes particularly strong when the sound converter is a soundreceiving unit such as a microphone, or when the area of the externalsound-transmitting port and/or the internal sound-transmitting port issmall. When the thickness of the waterproof sound-transmitting member 1is within the above range, the distance from the externalsound-transmitting port to the internal sound-transmitting port does notbecome excessively large even if the waterproof sound-transmittingmember 1 is placed. Therefore, the deterioration of the sound resultingfrom conversion by the sound converter can be inhibited.

The spacing distance between the waterproof sound-transmitting membrane2 and the support layer 3 in the non-joining region 4 is, for example,200 μm or less. The spacing distance may be 150 μm or less, 130 μm orless, 100 μm or less, less than 100 μm, or even 80 μm or less. The lowerlimit of the spacing distance is not limited, is, for example, 5 μm ormore, and may be 10 μm or more, 20 μm or more, or even 30 μm or more.When the spacing distance between the waterproof sound-transmittingmembrane 2 and the support layer 3 in the non-joining region 4 is withinthese ranges, deformation and permanent deformation of the waterproofsound-transmitting membrane 2 due to water pressure can be inhibitedmore reliably. In addition, the thickness of the waterproofsound-transmitting member 1 can be more reliably caused to fall withinthe above-described range.

The thickness of the support layer 3 in the non-joining region 4 is lessthan 100 μm. The thickness of the support layer 3 may be 99 μm or less,80 μm or less, 70 μm or less, 60 μm or less, 55 μm or less, 50 μm orless, 45 μm or less, or even 40 μm or less. The lower limit of thethickness is not limited, and is, for example, 2 μm or more. The supportlayer 3 can have the above thickness without being limited to thenon-joining region 4. The entirety of the support layer 3 may have theabove thickness. The fact that the thickness of the support layer 3 isless than 100 μm also contributes to a reduction in the thickness of thewaterproof sound-transmitting member 1.

The support layer 3 is not limited as long as the support layer 3 hasair permeability in the thickness direction thereof. The airpermeability in the thickness direction of the support layer 3 isnormally higher than the air permeability in the thickness direction ofthe waterproof sound-transmitting membrane 2. In addition, the strengthof the support layer 3 is normally higher than the strength of thewaterproof sound-transmitting membrane 2.

The material forming the support layer 3 is not limited, and examples ofthe material include: metals such as aluminum and stainless steel;resins such as polyolefins (polyethylene, polypropylene, etc.),polyesters (polyethylene terephthalate (PET), etc.), polyamides (variousaliphatic polyamides and aromatic polyamides including nylon, etc.), andpolyimides; and composite materials thereof.

The form of the support layer 3 is not limited, and is, for example, anonwoven fabric, a woven fabric, a net, a mesh, or a through-hole sheet.The net and the mesh have a lattice structure composed of skeletons andspaces between the skeletons (generally called “meshes”). The skeletonsof the lattice structure are composed of fibers such as filaments,wires, and tubes. The filaments may be monofilaments or multifilaments.In the present description, the mesh is used as a term meaning astructure in which fibers are woven, and the fibers three-dimensionallyintersect each at the intersections of the fibers (intersections of thelattice structure). The net is used as a term meaning a nonwovenstructure in which intersecting fibers are integrated at theintersection thereof.

The through-hole sheet is a sheet obtained by providing an originalsheet, for example, a non-porous sheet, which has a non-porous substratestructure, with a plurality of through holes (perforations) thatpenetrate the sheet in the thickness direction. The through-hole sheetmay be a sheet having no ventilation path in the thickness directionother than the plurality of through holes. The through holes may bestraight holes extending linearly in the thickness direction of thesheet. Whereas the meshes of the net and the mesh normally have apolygonal shape such as a quadrangular shape, the shapes of the openingsof the through holes are normally a circle or an ellipse when viewed ina direction perpendicular to a main surface of the through-hole sheet.The cross-sectional shape of each through hole may be uniform from onemain surface of the sheet to the other main surface of the sheet, or maychange from one main surface of the sheet to the other main surface ofthe sheet. The through holes may be formed such that the openingsthereof are regularly arranged or randomly located on the main surfaceof the sheet when viewed in the direction perpendicular to the mainsurface of the sheet. The through-hole sheet can be a metal sheet or aresin sheet. The through holes can be formed, for example, by lasermachining of the original sheet, or ion beam irradiation of the originalsheet followed by hole-formation processing with chemical etching. Withlaser machining, through holes having openings regularly arranged on themain surface when viewed in the direction perpendicular to the mainsurface of the sheet can be formed more reliably. As the through-holesheet, for example, the sheet disclosed in JP 2012-20279 A can be used.However, the sheet mayor may not be subjected to a liquid repellenttreatment.

Any combination of the material and the form of the support layer 3 canbe adopted.

The support layer 3 is preferably a mesh or a net, and particularlypreferably a mesh. The mesh and the net are suitable for maintainingstrength at a thickness less than 100 μm. Thus, in the waterproofsound-transmitting member 1 including the support layer 3 that is a meshor a net, deformation and permanent deformation of the waterproofsound-transmitting membrane 2 due to water pressure can be inhibitedmore reliably. In addition, in the case where the support layer 3 is amesh or a net, the rigidity and handleability of the waterproofsound-transmitting member 1 can be improved. Among them, the mesh issuitable for improving the sound transmission characteristics of thewaterproof sound-transmitting member 1.

The weight per unit area of the support layer 3 that is a mesh is, forexample, 25 to 70 g/m² in the case where the skeletons are composed of aresin such as PET. The lower limit of the weight per unit area may be 30g/m² or more, 35 g/m² or more, or even 38 g/m² or more. The upper limitof the weight per unit area may be 60 g/m² or less, 55 g/m² or less, oreven 45 g/m² or less. The weight per unit area of the support layer 3that is a mesh is, for example, 30 to 140 g/m² in the case where theskeletons are composed of a metal such as stainless steel. The lowerlimit of the weight per unit area may be 35 g/m² or more, 50 g/m² ormore, 60 g/m² or more, or even 70 g/m² or more. The upper limit of theweight per unit area may be 130 g/m or less, 120 g/m² or less, or even115 g/m² or less.

The waterproof sound-transmitting membrane 2 is not limited as long asthe waterproof sound-transmitting membrane 2 is a membrane that preventsentry of water while permitting sound to pass therethrough. Variousknown waterproof sound-transmitting membranes can be used as thewaterproof sound-transmitting membrane 2. The waterproofsound-transmitting membrane 2 may be subjected to a liquid repellenttreatment or an oil repellent treatment.

The waterproof sound-transmitting membrane 2 can be formed from a resinsuch as a polyester (for example, PET), a polycarbonate, a polyethylene,a polyimide, and PTFE. As the material of the waterproofsound-transmitting membrane 2, PTFE is suitable. A membrane formed fromPTFE (PTFE membrane) has good balance between mass and strength.

The PTFE membrane can be a porous membrane (porous PTFE membrane) formedby stretching a cast membrane or a paste extrusion containing PTFEparticles. The PTFE membrane may be sintered.

When the electronic device to which the waterproof sound-transmittingmember 1 is attached is expected to be exposed to higher water pressure,the PTFE membrane is preferably a microporous PTFE membrane or anon-porous PTFE membrane. Both the PTFE microporous membrane and thePTFE non-porous membrane can have a higher water entry pressure and havea lower degree of deformation due to water pressure.

In the present description, the microporous PTFE membrane refers to amembrane having an air permeability, in the thickness direction thereof,of 20 seconds/100 mL or more and 10,000 seconds/100 mL or less as an airpermeability (Gurley air permeability) measured according to Method B(Gurley method) of air permeability measurement specified in JapaneseIndustrial Standards (hereinafter, referred to as “JIS”) L1096. Thelower limit of the Gurley air permeability of the microporous PTFEmembrane may be greater than 30 seconds/100 mL, and may be 40seconds/100 mL or more, 50 seconds/100 mL or more, or even 70seconds/100 mL or more. The upper limit of the Gurley air permeabilityof the microporous PTFE membrane may be 5000 seconds/100 mL or less,1000 seconds/100 mL or less, or even 300 seconds/100 mL or less. In thepresent description, the non-porous PTFE membrane refers to a membranehaving an air permeability, in the thickness direction thereof, greaterthan 10,000 seconds/100 mL as the Gurley air permeability.

Even when the size of the waterproof sound-transmitting membrane 2 doesnot satisfy the recommended test piece size (about 50 mm×50 mm) in theGurley method, it is possible to evaluate the Gurley air permeability byusing a measurement jig. An example of the measurement jig is apolycarbonate disc provided with a through hole (having a circular crosssection with a diameter of 1 mm or 2 mm) at the center thereof andhaving a thickness of 2 mm and a diameter of 47 mm. Measurement of aGurley air permeability using the measurement jig can be performed asfollows.

A waterproof sound-transmitting membrane to be evaluated is fixed to onesurface of the measurement jig so as to cover the opening of the throughhole of the jig. The fixation is performed such that, during measurementof a Gurley air permeability, air passes through only the opening and aneffective test portion (portion overlapping the opening when viewed in adirection perpendicular to a main surface of the fixed waterproofsound-transmitting membrane) of the waterproof sound-transmittingmembrane to be evaluated, and the fixed portion of the waterproofsound-transmitting membrane does not hinder passing of air through theeffective test portion of the waterproof sound-transmitting membrane.For fixing the waterproof sound-transmitting membrane, a double-facedadhesive tape having a ventilation port punched in a center portionthereof with a shape that matches the shape of the opening can be used.The double-faced adhesive tape can be placed between the measurement jigand the waterproof sound-transmitting membrane such that thecircumference of the ventilation port and the circumference of theopening coincide with each other. Next, the measurement jig having thewaterproof sound-transmitting membrane fixed thereto is set on a Gurleyair permeability testing machine such that the surface on which thewaterproof sound-transmitting membrane is fixed is at the downstreamside of airflow during measurement, and a time t1 taken for air of 100mL to pass through the waterproof sound-transmitting membrane ismeasured. Next, the measured time t1 is converted into a value t pereffective test area of 642 [mm²] specified in Method B (Gurley method)of air permeability measurement in JIS L1096, by the equationt={(t1)×(area of effective test portion of waterproof sound-transmittingmembrane [mm²])/642 [mm²]}, and the obtained conversion value t can beregarded as the Gurley air permeability of the waterproofsound-transmitting membrane. When the above disc is used as themeasurement jig, the area of the effective test portion of thewaterproof sound-transmitting membrane is the area of a cross section ofthe through hole.

Condensation may occur inside the housing when the temperature of thehousing decreases due to, for example, use or mounting of the electronicdevice in water. The occurrence of condensation can be prevented byreducing the amount of water vapor staying inside the housing. In thecase where the waterproof sound-transmitting membrane 2 is a non-porousPTFE membrane, entry of water vapor into the housing through thewaterproof sound-transmitting membrane 2 is prevented. Therefore, byselecting a non-porous PTFE membrane as the waterproofsound-transmitting membrane 2, the amount of water vapor staying insidethe housing can be reduced, so that occurrence of condensation insidethe housing can be prevented.

Meanwhile, even if water vapor does not enter the inside of the housingthrough the waterproof sound-transmitting membrane 2, retention of watervapor inside the housing is unavoidable in some cases. Such a case is,for example, the case where the housing is formed from a resin havinghygroscopicity, such as polybutylene terephthalate (PBT),acrylonitrile-butadiene-styrene resin (ABS), polymethyl methacrylate(PMMA), polypropylene (PP), or polycarbonate (PC). In the housing formedfrom a resin having hygroscopicity, external water vapor absorbed by thehousing itself tends to be released to the inside of the housing by heatfrom a heat source inside the housing and stay inside the housing. Inthis case, to prevent occurrence of condensation in the housing, it ispreferable to select the waterproof sound-transmitting membrane 2capable of releasing water vapor staying inside the housing to theoutside. An example of the selectable waterproof sound-transmittingmembrane 2 is a microporous PTFE membrane. When the waterproofsound-transmitting membrane 2 is a microporous PTFE membrane, it ispossible to discharge retained water vapor to the outside due to theappropriate air permeability of the membrane 2 even though highwaterproofness is achieved, so that occurrence of condensation insidethe housing can be prevented.

The average pore diameter of the waterproof sound-transmitting membrane2 that is a microporous PTFE membrane is, for example, 0.01 to 1 μm. Theporosity of the waterproof sound-transmitting membrane 2 that is amicroporous PTFE membrane is, for example, 5 to 50%. The average porediameter of the PTFE membrane can be measured according to AmericanSociety for Testing and Materials (ASTM) F316-86. The porosity of thePTFE membrane can be calculated by substituting the mass, the thickness,the area (area of a main surface), and the true density of the membraneinto the following equation. The true density of PTFE is 2.18 g/cm³.

Porosity (%)={1−(mass [g]/(thickness [cm]×area [cm²]×true density [2.18g/cm³]))}×100

The thickness of the waterproof sound-transmitting membrane 2 is, forexample, 1 to 50 μm. The thickness of the waterproof sound-transmittingmembrane 2 may be 3 to 30 μm or 5 to 20 μm. When the thickness of thewaterproof sound-transmitting membrane 2 is within these ranges, thewaterproofness and the sound transmission characteristics of thewaterproof sound-transmitting membrane 2 can be improved in awell-balanced manner.

The surface density of the waterproof sound-transmitting membrane 2 is,for example, 1 to 30 g/m². The surface density of the waterproofsound-transmitting membrane 2 may be 1 to 25 g/m². The surface densitycan be calculated by dividing the mass of the waterproofsound-transmitting membrane 2 by the area (area of a main surface) ofthe waterproof sound-transmitting membrane 2.

The waterproofness of the waterproof sound-transmitting membrane 2 canbe evaluated on the basis of water entry pressure (limit water entrypressure). The water entry pressure of the waterproof sound-transmittingmembrane 2 is, for example, 80 kPa or more. The water entry pressure ofthe waterproof sound-transmitting membrane 2 may be 100 kPa or more, 300kPa or more, 500 kPa or more, 600 kPa or more, 700 kPa or more, 750 kPaor more, 800 kPa or more, 900 kPa or more, or even 1000 kPa or more. Theupper limit of the water entry pressure is not limited, and is, forexample, 2000 kPa or less. The water entry pressure of the waterproofsound-transmitting membrane 2 can be measured as follows according toMethod A (low water pressure method) or Method B (high water pressuremethod) of the water resistance test in JIS L1092 using a measurementjig.

An example of the measurement jig is a stainless disc having a diameterof 47 mm and provided with a through hole (having a circular crosssection) having a diameter of 1 mm at the center thereof. The disc has athickness sufficient to prevent the disc from deforming due to the waterpressure applied upon measurement of a water entry pressure. Measurementof a water entry pressure using the measurement jig can be performed asfollows.

A waterproof sound-transmitting membrane to be evaluated is fixed to onesurface of the measurement jig so as to cover the opening of the throughhole of the jig. The fixation is performed such that, during measurementof a water entry pressure, water does not leak from a fixed portion ofthe membrane. For fixing the waterproof sound-transmitting membrane, adouble-faced adhesive tape having a water port punched in a centerportion thereof with a shape that matches the shape of the opening canbe used. The double-faced adhesive tape can be placed between themeasurement jig and the waterproof sound-transmitting membrane such thatthe circumference of the water port and the circumference of the openingcoincide with each other. Next, the measurement jig having thewaterproof sound-transmitting membrane fixed thereto is set on a testingdevice such that the surface opposite to the membrane-fixed surface ofthe measurement jig is a water pressure application surface to whichwater pressure is applied during measurement, and a water entry pressureis measured according to Method A (low water pressure method) or MethodB (high water pressure method) of the water resistance test in JISL1092. The water entry pressure is measured on the basis of the waterpressure when water comes out from one spot on the membrane surface ofthe waterproof sound-transmitting membrane. The measured water entrypressure can be regarded as the water entry pressure of the waterproofsound-transmitting membrane. As the testing device, a device that hasthe same configuration as the water resistance testing deviceexemplified in JIS L1092 and that has a test piece attachment structurecapable of setting the measurement jig can be used.

The sound transmission characteristics of the waterproofsound-transmitting membrane 2 can be evaluated on the basis of insertionloss at 1 kHz (insertion loss for sound having a frequency of 1 kHz).The insertion loss at 1 kHz of the waterproof sound-transmittingmembrane 2 is, for example, 17 dB or less, and can be 13 dB or less, 10dB or less, 8 dB or less, 7 dB or less, or even 6 dB or less, when thearea of the sound-transmission region of the membrane is 1.8 mm².

The sound transmission characteristics of the waterproofsound-transmitting membrane 2 can also be evaluated on the basis ofinsertion loss at 200 Hz (insertion loss for sound having a frequency of200 Hz). The insertion loss at 200 Hz of the waterproofsound-transmitting membrane 2 is, for example, 13 dB or less, and can be11 dB or less, 10 dB or less, or even 8 dB or less, when the area of thesound-transmission region of the membrane is 1.8 mm².

Regarding the waterproof sound-transmitting membrane 2, the degree ofdecrease in sound transmission characteristics due to water pressure canbe evaluated on the basis of the sound transmission characteristicsdecrease rate (insertion loss change rate) obtained from the insertionlosses of the waterproof sound-transmitting membrane 2 before and aftera water pressure retention test. The water pressure retention test is atest in which a constant water pressure is applied to a waterproofsound-transmitting membrane for a fixed time (water pressure applicationtime). The water pressure retention test can be performed using themeasurement jig and the water resistance testing device for measuringthe water entry pressure of a waterproof sound-transmitting membrane.More specifically similar to the case of measuring a water entrypressure, the measurement jig having the waterproof sound-transmittingmembrane fixed thereto may be set on the testing device such that thesurface opposite to the membrane-fixed surface of the measurement jig isa water pressure application surface, and a constant water pressure maybe applied to the waterproof sound-transmitting membrane for a fixedtime. In the case of evaluating whether water leakage occurs at thewaterproof sound-transmitting membrane during the test, if water comesout from one spot on the membrane surface of the waterproofsound-transmitting membrane, it is determined that “water leakageoccurs”. The water pressure applied to the waterproof sound-transmittingmembrane during the test is not limited, and is, for example, 50 kPa to1000 kPa. The water pressure application time is, for example, 10 to 30minutes. The sound transmission characteristics decrease rate can bedetermined by the following equation. In the following equation, L1 isthe insertion loss (for example, insertion loss at 1 kHz) of thewaterproof sound-transmitting membrane before the test, and L2 is theinsertion loss (for example, insertion loss at 1 kHz) of the waterproofsound-transmitting membrane after the test.

Sound transmission characteristics decrease rate (%)=(L2−L1)/L1×100

The sound transmission characteristics decrease rate of the waterproofsound-transmitting membrane 2 obtained from the insertion losses beforeand after the water pressure retention test (water pressure: 500 kPa,water pressure application time: 10 minutes) (calculated on the basis ofinsertion loss at 1 kHz) is, for example, 50% or less, and can be 40% orless, 30% or less, or even 25% or less.

In the example shown in FIG. 1A and FIG. 1B, the waterproofsound-transmitting membrane 2 is a single-layer membrane. The waterproofsound-transmitting membrane 2 may be a laminate of two or moremembranes. The waterproof sound-transmitting membrane 2 can be alaminate of two or more PTFE membranes.

The waterproof sound-transmitting membrane 2 may be a colored membrane.The waterproof sound-transmitting membrane 2 may be colored, forexample, in gray or black. The gray or black waterproofsound-transmitting membrane 2 can be formed, for example, by mixing agray or black coloring agent with the material forming the membrane. Theblack coloring agent is, for example, carbon black. A color in the rangeof 1 to 4 and a color in the range of 5 to 8 as represented by“achromatic color brightness NV” defined in JIS Z8721 can be defined as“black” and “gray”, respectively.

The configuration of the joining portion 6 is not limited as long as thejoining region 5 and the non-joining region 4 can be formed. The joiningportion 6 is, for example, a pressure-sensitive adhesive layer or anadhesive layer. The joining portion 6 that is a pressure-sensitiveadhesive layer or an adhesive layer can be formed, for example byapplying a known pressure-sensitive adhesive or a known adhesive to thesurface of the waterproof sound-transmitting membrane 2. The joiningportion 6 may be composed of a double-faced adhesive tape. That is, inthe joining region 5, the waterproof sound-transmitting membrane 2 andthe support layer 3 may be joined by a double-faced adhesive tape. Inthe case where the joining portion 6 is composed of a double-facedadhesive tape, the waterproof sound-transmitting membrane 2 and thesupport layer 3 are joined more reliably, so that the waterproofness ofthe waterproof sound-transmitting member 1 can be further improved. Inaddition, the spacing distance between the waterproof sound-transmittingmembrane 2 and the support layer 3 in the non-joining region 4 can bemore easily controlled.

As the double-faced adhesive tape forming the joining portion 6, a knowndouble-faced adhesive tape can be used. The substrate of thedouble-faced adhesive tape is, for example, a film, a nonwoven fabric,or a foam of a resin. The resin that can be used for the substrate arenot limited, and examples of the resin include polyesters (PET, etc.),polyolefins (polyethylene, etc.), and polyimides. For thepressure-sensitive adhesive layer of the double-faced adhesive tape,various pressure-sensitive adhesives such as acrylic-basedpressure-sensitive adhesives and silicone-based pressure-sensitiveadhesives can be used. Acrylic-based pressure-sensitive adhesives arepreferably used for the pressure-sensitive adhesive layer since thejoining strength between the waterproof sound-transmitting membrane 2and the support layer 3 can be improved. The double-faced adhesive tapemay be a thermal adhesive tape.

The thickness of the joining portion 6 is, for example, 200 μm or less.The thickness of the joining portion 6 may be 150 μm or less, 130 μm orless, 100 μm or less, less than 100 μm, or even 80 μm or less. The lowerlimit of the thickness of the joining portion 6 is not limited, is, forexample, 5 μm or more, and may be 10 μm or more, 20 μm or more, or even30 μm or more. When the thickness of the joining portion 6 is withinthese ranges, the spacing distance between the waterproofsound-transmitting membrane 2 and the support layer 3 in the non-joiningregion 4 can be controlled to be within the above-described preferablerange, and deformation and permanent deformation of the waterproofsound-transmitting membrane 2 due to water pressure can be inhibitedmore reliably.

The waterproof sound-transmitting member 1 can be placed between ahousing of an electronic device and a sound converter housed in thehousing. The waterproof sound-transmitting member 1 is normally fixed toan inner wall surface of the housing so as to cover an externalsound-transmitting port. In addition, the waterproof sound-transmittingmember 1 can be fixed to a housing of the sound converter or the surfaceof a substrate having the sound converter so as to cover an internalsound-transmitting port. The positional relationship between: theexternal sound-transmitting port and the internal sound-transmittingport; and the non-joining region 4 of the waterproof sound-transmittingmember 1 in the fixed state is not limited as long as sound can betransmitted between the outside and the sound converter. The externalsound-transmitting port and the internal sound-transmitting port, andthe non-joining region 4 in the fixed state may overlap each other whenviewed in the direction perpendicular to the main surface of thewaterproof sound-transmitting membrane 2.

The method for fixing the waterproof sound-transmitting member 1 to thehousing and the sound converter is not limited. The waterproofsound-transmitting member 1 can be fixed to the housing and/or the soundconverter by various kinds of welding such as heat welding, ultrasonicwelding, and laser welding, or adhesion using a pressure-sensitiveadhesive, an adhesive, or the like. It is also possible to fix thewaterproof sound-transmitting member 1 by a fixing portion composed of apressure-sensitive adhesive layer, an adhesive layer, or a double-facedadhesive tape. Among them, in the case where the fixing portion iscomposed of a double-faced adhesive tape, the waterproofsound-transmitting member 1 can be more reliably fixed to the housingand the sound converter. As the double-faced adhesive tape forming thefixing portion, the double-faced adhesive tape described above in thedescription of the joining portion 6 can be used. Regarding thewaterproof sound-transmitting member 1 fixed to both the housing and thesound converter, the method for fixing to the housing and the method forfixing to the sound converter may be the same or different from eachother.

FIG. 2 shows an example of the waterproof sound-transmitting member ofthe present invention further including a fixing portion 7A. In thewaterproof sound-transmitting member 1 shown in FIG. 2, the fixingportion 7A is placed on the surface, of the waterproofsound-transmitting membrane 2, opposite to the surface, of thewaterproof sound-transmitting membrane 2, joined to the support layer 3.The fixing portion 7A includes the region of the peripheral portion ofthe waterproof sound-transmitting membrane 2 when viewed in thedirection perpendicular to the main surface of the waterproofsound-transmitting membrane 2. The fixing portion 7A has the same shapeas the joining region 5 when viewed in the perpendicular direction. Thefixing portion 7A has an opening 8 with a shape corresponding to thenon-joining region 4, when viewed in the perpendicular direction. Soundis mainly transmitted through the opening 8 of the fixing portion 7A.The opening 8 is a sound-transmission region of the waterproofsound-transmitting membrane 2 and the waterproof sound-transmittingmember 1. The opening 8 coincides with the non-joining region 4 whenviewed in the perpendicular direction. The waterproof sound-transmittingmember 1 shown in FIG. 2 can be fixed to the housing by the fixingportion 7A. The shape of the opening 8 of the fixing portion 7A may bethe same as that of the external sound-transmitting port of the housing.In this case, the waterproof sound-transmitting member 1 can be fixed tothe housing such that the circumference of the opening 8 and thecircumference of the external sound-transmitting port coincide with eachother when viewed in the perpendicular direction.

FIG. 3 shows another example of the waterproof sound-transmitting memberof the present invention further including the fixing portion 7A. Thewaterproof sound-transmitting member 1 shown in FIG. 3 is the same asthe waterproof sound-transmitting member 1 shown in FIG. 2, except thatthe shape of the fixing portion 7A is different. The fixing portion 7Aof the waterproof sound-transmitting member 1 shown in FIG. 3 has anopening 8 that is larger than the non-joining region 4 and overlaps thenon-joining region 4 (more specifically, includes the non-joining region4) when viewed in the perpendicular direction. Also, in the waterproofsound-transmitting member 1 shown in FIG. 3, the shape of the opening 8of the fixing portion 7A may be the same as that of the externalsound-transmitting port of the housing. In the waterproofsound-transmitting member 1 shown in FIG. 3, it is possible to make thearea of the non-joining region 4 smaller than the area of the externalsound-transmitting port. Thus, the waterproof performance of theelectronic device to which the waterproof sound-transmitting member 1 isfixed can be further enhanced.

FIG. 4 shows an example of the waterproof sound-transmitting member ofthe present invention further including a fixing portion 7B. In thewaterproof sound-transmitting member 1 shown in FIG. 4, the fixingportion 7B is placed on the surface, of the support layer 3, opposite tothe surface, of the support layer 3, joined to the waterproofsound-transmitting membrane 2. The fixing portion 7B can have the sameshape as the fixing portion 7A shown in FIG. 2 or FIG. 3 when viewed inthe direction perpendicular to the main surface of the waterproofsound-transmitting membrane 2. The waterproof sound-transmitting member1 shown in FIG. 4 can be fixed to the sound converter by the fixingportion 7B.

FIG. 5 shows an example of the waterproof sound-transmitting member ofthe present invention further including the fixing portions 7A and 7B.In the waterproof sound-transmitting member 1 shown in FIG. 5, thefixing portion 7A is placed on the surface, of the waterproofsound-transmitting membrane 2, opposite to the surface, of thewaterproof sound-transmitting membrane 2, joined to the support layer 3.In addition, the fixing portion 7B is placed on the surface, of thesupport layer 3, opposite to the surface, of the support layer 3, joinedto the waterproof sound-transmitting membrane 2. The fixing portions 7Aand 7B can have the same shape as the fixing portion 7A shown in FIG. 2or FIG. 3 when viewed in the direction perpendicular to the main surfaceof the waterproof sound-transmitting membrane 2. The shape of the fixingportion 7A and the shape of the fixing portion 7B may be the same ordifferent from each other. The waterproof sound-transmitting member 1shown in FIG. 5 can be fixed to the housing by the fixing portion 7A andcan be fixed to the sound converter by the fixing portion 7B.

The shapes of the fixing portions 7A and 7B are not limited to the aboverespective examples. However, the fixing portions 7A and 7B eachpreferably have a shape in which the fixing portion 7A or 7B is includedin the joining region 5 when viewed in the direction perpendicular tothe main surface of the waterproof sound-transmitting membrane 2, sincesound is mainly transmitted through the openings 8 of the fixingportions 7A and 7B. The thickness of the waterproof sound-transmittingmember 1 further including the fixing portion 7A and/or 7B is determinedincluding the thickness of the fixing portion.

The waterproof sound-transmitting member of the present invention canhave any layer other than the above-described layers, and/or a member,as long as the advantageous effects of the present invention areobtained.

The waterproofness of the waterproof sound-transmitting member 1 can beevaluated on the basis of water entry pressure (limit water entrypressure). The water entry pressure of the waterproof sound-transmittingmember 1 can be measured according to the above-described method formeasuring the water entry pressure of the waterproof sound-transmittingmembrane 2. However, upon the measurement, the water pressure is appliedto the waterproof sound-transmitting member 1 from the waterproofsound-transmitting membrane 2 side. The water entry pressure of thewaterproof sound-transmitting member 1 is higher than the water entrypressure of the waterproof sound-transmitting membrane 2.

The waterproofness of the waterproof sound-transmitting member 1 canalso be evaluated by a water pressure retention test. The water pressureretention test can be performed in the same manner as the water pressureretention test for the waterproof sound-transmitting membrane. However,in the test, the water pressure is applied to the waterproofsound-transmitting member 1 from the waterproof sound-transmittingmembrane 2 side. The waterproof sound-transmitting member 1 can be amember in which water leakage does not occur at the waterproofsound-transmitting membrane 2 even when the water pressure retentiontest is performed under the conditions of a water pressure of 60 kPa anda water pressure application time of 10 minutes. The waterproofsound-transmitting member 1 can be a member in which water leakage doesnot occur at the waterproof sound-transmitting membrane 2 even when thewater pressure retention test is performed under the conditions of awater pressure of 500 kPa and a water pressure application time of 10minutes. The waterproof sound-transmitting member 1 can be a member inwhich water leakage does not occur at the waterproof sound-transmittingmembrane 2 even when the water pressure retention test is performedunder the conditions of a water pressure of 700 kPa and a water pressureapplication time of 30 minutes. The waterproof sound-transmitting member1 can be a member in which water leakage does not occur at thewaterproof sound-transmitting membrane 2 even when the water pressureretention test is performed repeatedly 30 times under the conditions ofa water pressure of 700 kPa and a water pressure application time of 30minutes with the interval between each test being set as 1 minute.

The sound transmission characteristics of the waterproofsound-transmitting member 1 can be evaluated on the basis of insertionloss at 1 kHz (insertion loss for sound having a frequency of 1 kHz).The insertion loss at 1 kHz of the waterproof sound-transmitting member1 is, for example, 17 dB or less, and can be 13 dB or less, 10 dB orless, 9 dB or less, 8 dB or less, 7 dB or less, or even 6.5 dB or less,when the area of the non-joining region 4 is 1.8 mm².

The sound transmission characteristics of the waterproofsound-transmitting member 1 can also be evaluated on the basis ofinsertion loss at 200 Hz (insertion loss for sound having a frequency of200 Hz). The insertion loss at 200 Hz of the waterproofsound-transmitting member 1 is, for example, 14 dB or less, and can be12 dB or less, 11 dB or less, 10 dB or less, or even 9 dB or less, whenthe area of the non-joining region 4 is 1.8 mm².

The sound transmission characteristics of the waterproofsound-transmitting member 1 can also be evaluated on the basis of anincrement of the insertion loss of the waterproof sound-transmittingmember 1 (increment with respect to the waterproof sound-transmittingmembrane alone) with respect to the insertion loss of the waterproofsound-transmitting membrane 2 (the insertion loss of the waterproofsound-transmitting membrane 2 itself measured without placing thesupport layer 3). The increment can be determined by the equation:[increment of insertion loss]=[insertion loss of waterproofsound-transmitting member 1]−[insertion loss of waterproofsound-transmitting membrane 2]. The increment of the insertion loss at 1kHz of the waterproof sound-transmitting member 1 is, for example, 5 dBor less, and can be 4 dB or less, 2 dB or less, 1.5 dB or less, or even1 dB or less, when the area of the non-joining region 4 is 1.8 mm². Theincrement of the insertion loss at 200 Hz of the waterproofsound-transmitting member 1 is, for example, 10 dB or less, and can be 6dB or less, 5 dB or less, 4 dB or less, 2 dB or less, 1.5 dB or less, oreven 1 dB or less, when the area of the non-joining region 4 is 1.8 mm².Particularly, in the case where the support layer 3 is a mesh, theincrement can be decreased.

In the waterproof sound-transmitting member 1, a decrease in soundtransmission characteristics due to water pressure can be inhibited.Even after the water pressure retention test under the conditions of awater pressure of 500 kPa and a water pressure application time of 10minutes, the waterproof sound-transmitting member 1 exhibits, forexample, an insertion loss at 1 kHz of 11 dB or less when the area ofthe non-joining region 4 is 1.8 mm². The insertion loss can be 10 dB orless, 9 dB or less, 7 dB or less, or even 6.5 dB or less.

The sound transmission characteristics decrease rate of the waterproofsound-transmitting member 1 obtained from the insertion losses beforeand after the water pressure retention test (water pressure: 500 kPa,water pressure application time: 10 minutes) (calculated on the basis ofinsertion loss at 1 kHz) is, for example, less than 6.6%, and can be6.0% or less, 5.5% or less, 5.0% or less, 4.0% or less, 3.0% or less,2.0% or less, 1.5% or less, or even 1.0% or less. The sound transmissioncharacteristics decrease rate of the waterproof sound-transmittingmember can be evaluated according to the above method for evaluating thesound transmission characteristics decrease rate of the waterproofsound-transmitting membrane, except that the object to be measured forinsertion loss is changed from the waterproof sound-transmittingmembrane to the waterproof sound-transmitting member.

The waterproof sound-transmitting member 1 can be supplied, for example,in a state of being placed on a sheet-shaped base film, or in a state ofbeing placed on a band-shaped base film and wound on a roll or a reel.The fixing portion 7A or the fixing portion 7B can be used for placingthe waterproof sound-transmitting member 1 onto the base film. A peelinglayer that allows the waterproof sound-transmitting member 1 to beeasily peeled from the base film may be formed on the surface, of thebase film, on which the waterproof sound-transmitting member 1 isplaced. As the base film, for example, a polymer film, paper, a metalfilm, and composite films thereof can be used. FIG. 6 shows an exampleof a state where the waterproof sound-transmitting member 1 is placed onthe base film. In the example shown in FIG. 6, the waterproofsound-transmitting member 1 is placed on a base film 11 with the fixingportion 7A interposed therebetween. In addition, the waterproofsound-transmitting member 1 shown in FIG. 6 includes, on the fixingportion 7B, a separator 12 for protecting the fixing portion 7B and thenon-joining region 4. When the waterproof sound-transmitting member 1 isused, the separator 12 is peeled off.

The application of the waterproof sound-transmitting member 1 is notlimited. The waterproof sound-transmitting member 1 can be used forapplications requiring both sound transmission and waterproofness, forexample, a waterproof sound-transmitting structure, an article having awaterproof sound-transmitting structure, etc. The waterproofsound-transmitting member 1 is typically used for an electronic devicehaving an audio function.

FIG. 7 shows an example of an electronic device for which the waterproofsound-transmitting member 1 is used. The electronic device shown in FIG.7 is a smartphone 20. Sound converters that perform conversion betweenan electric signal and sound are placed inside a housing 22 of thesmartphone 20. The sound converters are, for example, a speaker and amicrophone. The housing 22 is provided with an opening 23 and an opening24 that are external sound-transmitting ports.

In the smartphone 20, a first waterproof sound-transmitting member 1 isfixed to an inner wall surface of the housing 22 so as to cover theopening 23. In addition, a second waterproof sound-transmitting member 1is fixed to the inner wall surface of the housing 22 so as to cover theopening 24. In each waterproof sound-transmitting member 1, the surfaceat the waterproof sound-transmitting membrane 2 side faces the outsidethrough the opening 23 or 24. In addition, the non-joining region 4 ofeach waterproof sound-transmitting member 1 overlaps the opening 23 orthe opening 24 when viewed in the direction perpendicular to the mainsurface of the waterproof sound-transmitting membrane 2.

Each of the first and second waterproof sound-transmitting members 1 isfixed to the sound converter housed in the housing (not shown). In eachwaterproof sound-transmitting member 1, the surface of the support layer3 side is in contact with the sound converter. In addition, thenon-joining region 4 of each waterproof sound-transmitting member 1 andan internal sound-transmitting port of the sound converter to which eachwaterproof sound-transmitting member 1 is fixed overlap each other whenviewed in the direction perpendicular to the main surface of thewaterproof sound-transmitting membrane 2.

The sound converters (sound conversion parts) are, for example, aspeaker and a microphone. Each sound converter may be a microphone.

The electronic device for which the waterproof sound-transmitting member1 can be used is not limited to the smartphone 20. Examples of theelectronic device include: wearable devices such as a smart watch and awristband; various cameras including an action camera and a securitycamera; communication devices such as a mobile phone and a smartphone;virtual reality (VR) devices; augmented reality (AR) devices; and sensordevices.

In the case where the waterproof sound-transmitting membrane 2 has airpermeability in the thickness direction thereof, the waterproofsound-transmitting member 1 can also be used as a waterproofair-permeable member. In this case, the waterproof sound-transmittingmembrane 2 serves as a waterproof air-permeable membrane that preventsentry of water while permitting gas to pass therethrough. The waterproofair-permeable member can be attached to the housing such that thewaterproof air-permeable member covers an opening (ventilation port)connecting the inside and the outside of the housing and the waterproofair-permeable membrane side of the waterproof air-permeable member facesthe outside (external space). The waterproof air-permeable memberincluding the waterproof air-permeable membrane can prevent entry ofwater into the housing through the opening in the electronic devicewhile allowing ventilation between the inside and the outside of thehousing through the opening. The electronic device does not have to havea sound conversion part. In addition, when water pressure is applied tothe opening of the electronic device to which the waterproofair-permeable member is attached, the waterproof air-permeable membranebecomes deformed in the direction to the support layer 3 (direction fromthe outside to the inside of the housing) in the non-joining region 4.However, in the waterproof air-permeable member, deformation of thewaterproof air-permeable membrane is limited in a certain range bycontact between the deformed waterproof air-permeable membrane and thesupport layer 3, so that breaking of the waterproof air-permeablemembrane is prevented. Therefore, since the support layer 3 is included,the waterproof air-permeable member can have waterproofness (forexample, limit water entry pressure) higher than the waterproofness ofthe waterproof air-permeable membrane.

The permanent deformation that remains in the waterproof air-permeablemembrane even after being released from the water pressure decreases theair-permeability characteristics of the waterproof air-permeable member,and, for example, variation in air permeability occurs, or deviationfrom the air-permeability characteristics designed for the waterproofair-permeable member occurs. The support layer 3 can reduce thepermanent deformation by limiting deformation of the waterproofair-permeable membrane. For example, in the case where the electronicdevice is a sensor device such as a pressure sensor, variation in airpermeability and deviation from the designed air-permeabilitycharacteristics may adversely affect the performance of the device.

Furthermore, when the thickness of the support layer 3 in thenon-joining region 4 is less than 100 μm, the responsiveness of airpermeation of the waterproof air-permeable member can be improved. Theimproved responsiveness of air permeation is particularly advantageouswhen the electronic device is a sensor device such as a pressure sensor.

The waterproof member of the present invention that is a waterproofair-permeable member can have the same configuration as the waterproofsound-transmitting member 1 as long as the waterproof membrane has airpermeability in the thickness direction thereof. As the waterproofair-permeable membrane included in the waterproof air-permeable member,a membrane having air permeability in the thickness direction thereofcan be selected from among the waterproof sound-transmitting membranes 2described above. In addition, the waterproof member of the presentinvention that is a waterproof air-permeable member can have the samecharacteristics as the waterproof sound-transmitting member 1.

In the waterproof member of the present invention that is a waterproofair-permeable member, deviation of the air-permeability characteristicsdue to water pressure can be inhibited. The degree of change inair-permeability characteristics before and after the water pressureretention test (water pressure: 500 kPa, water pressure applicationtime: 10 minutes) is, for example, 5% or less, and can be 4% or less, 3%or less, 2% or less, or even 1% or less. The degree of change inair-permeability characteristics of the waterproof air-permeable membercan be determined by the formula: |(AP2-AP1)|/AP1×100(%), where the airpermeability of the waterproof air-permeable member (air permeability inthe direction of permeation through the waterproof air-permeablemembrane and the support layer 3) before the water pressure retentiontest is AP1 and the air permeability of the waterproof air-permeablemember after the water pressure retention test is AP2. In addition, theair permeability of the waterproof air-permeable member can be obtainedas an air resistance (unit: seconds/100 mL) according to the Oken typetesting machine method specified in JIS P8117: 2009. The recommendedtest piece size in the Oken type testing machine method is 50 mm×50 mm.Even when the size of a waterproof air-permeable member to be evaluateddoes not satisfy the recommended size, evaluation of air resistanceaccording to the Oken type testing machine method is possible by using ameasurement jig.

The measurement jig has a shape and a size that allow the measurementjig to be placed on an air permeability measuring portion of the Okentype testing machine, and the thickness and the material of themeasurement jig are a thickness and a material that do not change by adifferential pressure applied to a test piece upon measurement of airresistance. An example of the measurement jig is a polycarbonate dischaving a thickness of 2 mm and a diameter of 47 mm. A through holehaving an opening with a smaller size than a waterproof air-permeablemember to be evaluated is provided at the center in a surface of themeasurement jig. The through hole typically has a circular cross-sectionand has a diameter that allows the opening of the through hole to befully covered with the waterproof air-permeable member to be evaluated.As the diameter of the through hole, for example, 1 mm or 2 mm can beadopted. Next, the waterproof air-permeable member to be evaluated isfixed to one surface of the measurement jig so as to cover the opening.The fixation is performed such that, during measurement of airresistance, air passes through only the non-joining region 4, and thefixed portion does not hinder passing of air in the non-joining region4. The waterproof air-permeable membrane may face the measurement jigside, or the support layer 3 may face the measurement jig side. Forfixing the waterproof air-permeable member, a double-faced adhesive tapehaving a ventilation port punched in a center portion thereof with ashape that matches the shape of the opening can be used. Thedouble-faced adhesive tape can be placed between the measurement jig andthe waterproof air-permeable member such that the circumference of theventilation port and the circumference of the opening coincide with eachother. Next, the measurement jig having the waterproof air-permeablemember fixed thereto is set on the air permeability measuring portion ofthe Oken type testing machine such that the fixed surface of the memberis at the downstream side of airflow during measurement, a test by theOken type testing machine method is conducted, and an air resistanceindication value t2 indicated by the testing machine is recorded. Next,the recorded air resistance indication value t2 is converted into avalue t_(K) per effective test area of 6.452 [cm²] specified in the Okentype testing machine method, by the equation t_(K)={t2×(area ofnon-joining region 4 [cm²])/6.452 [cm²]}, and the obtained conversionvalue t_(K) can be regarded as the air resistance of the waterproofair-permeable member measured according to the Oken type testing machinemethod.

Examples of the electronic device for which the waterproof member of thepresent invention that is a waterproof air-permeable member can be usedinclude sensor devices such as a pressure sensor, a flow rate sensor,and a gas concentration sensor (O₂ sensor, etc.). However, theelectronic device is not limited to the above examples.

As described above, the waterproof member of the present invention maybe a waterproof sound-transmitting member including a waterproofsound-transmitting membrane configured to prevent entry of water whilepermitting sound to pass therethrough, and a support layer having airpermeability in a thickness direction thereof, wherein

the member has

-   -   a joining region where the waterproof sound-transmitting        membrane and the support layer are joined, and    -   a non-joining region where the waterproof sound-transmitting        membrane and the support layer are spaced apart from each other,

the non-joining region is surrounded by the joining region when viewedin a direction perpendicular to a main surface of the waterproofsound-transmitting membrane, and

a thickness of the support layer in the non-joining region is less than100 μm.

Moreover, the waterproof member of the present invention may be awaterproof air-permeable member including a waterproof air-permeablemembrane configured to prevent entry of water while permitting gas topass therethrough, and a support layer having air permeability in athickness direction thereof, wherein

the member has

-   -   a joining region where the waterproof air-permeable membrane and        the support layer are joined, and    -   a non-joining region where the waterproof air-permeable membrane        and the support layer are spaced apart from each other,

the non-joining region is surrounded by the joining region when viewedin a direction perpendicular to a main surface of the waterproofair-permeable membrane, and

a thickness of the support layer in the non-joining region is less than100 μm.

EXAMPLES

Hereinafter, the present invention will be described more specificallyby way of Examples. The present invention is not limited to thefollowing Examples. In the following Examples, for convenience,membranes that can be used as air-permeable membranes are also referredto as sound-transmitting membranes.

(Preparation of Waterproof Sound-Transmitting Membrane)

The following sound-transmitting membranes A to C were prepared aswaterproof sound-transmitting membranes.

[Sound-Transmitting Membrane A]

1 part by mass of a fluorine-based surfactant (MEGAFAC F-142D,manufactured by DIC) per 100 parts by mass of PTFE was added to a PTFEdispersion that is a dispersion liquid of PTFE particles (concentrationof PTFE particles: 40% by mass, average particle diameter of PTFEparticles: 0.2 μm, containing 6 parts by mass of a nonionic surfactantper 100 parts by mass of PTFE). Next, a coating membrane (thickness: 20μm) of the above PTFE dispersion containing the fluorine-basedsurfactant was formed on the surface of a band-shaped polyimidesubstrate (thickness: 125 μm). The coating membrane was formed byimmersing the polyimide substrate in the PTFE dispersion and thenpulling up the polyimide substrate. Next, the entirety of the substrateand the coating membrane was heated to form a cast PTFE membrane. Theheating was performed in two stages, first heating (100° C., 1 minute)and subsequent second heating (390° C., 1 minute). The first heatingpromoted removal of the dispersion medium contained in the coatingmembrane, and the second heating promoted the formation of the castmembrane based on binding of the PTFE particles contained in the coatingmembrane. The above immersion and subsequent heating were repeatedfurther twice, and the formed PTFE cast membrane (thickness: 25 μm) wasthen peeled from the polyimide substrate.

Next, the peeled cast membrane was rolled in an MD direction(longitudinal direction) and further stretched in a TD direction (widthdirection). The rolling in the MD direction was performed by rollrolling. The rolling ratio (area ratio) was set to 2.0 times, and thetemperature (roll temperature) was set to 170° C. The stretching in theTD direction was performed with a tenter stretching machine. The stretchratio in the TD direction was set to 2.0 times, and the temperature(temperature of stretching atmosphere) was set to 300° C. Thus, thesound-transmitting membrane A which is a microporous PTFE membrane wasobtained.

The thickness of the obtained sound-transmitting membrane A was 10 μm,the surface density thereof was 14.5 g/m², the porosity thereof was 30%,the air permeability in the thickness direction thereof was 100seconds/100 mL as represented by a Gurley air permeability, and thewater entry pressure (limit water entry pressure) thereof was 1600 kPa.

[Sound-Transmitting Membrane B]

100 parts by mass of PTFE fine powder (F104, manufactured by DaikinIndustries, Ltd.) and 20 parts by mass of n-dodecane (manufactured byJXTG Nippon Oil & Energy Corporation) as a molding aid were uniformlymixed. Next, the obtained mixture was compressed using a cylinder, thenformed into a sheet by ram extrusion, and further rolled by rollrolling. Next, the obtained sheet (thickness: 0.2 mm) was heated at 150°C. to remove the molding aid by drying to obtain a PTFE sheet moldedbody.

Next, the obtained sheet molded body was stretched in the MD direction(rolling direction) at a stretching temperature of 260° C. and a stretchratio of 10 times, and then stretched in the TD direction (widthdirection) at a stretching temperature of 150° C. and a stretch ratio of15 times. Then, the entire sheet molded body was sintered at 360° C.,which is higher than the melting point of PTFE (327° C.), to obtain thesound-transmitting membrane B which is a PTFE porous membrane.

The thickness of the obtained sound-transmitting membrane B was 4 μm,the surface density thereof was 5.0 g/m², the porosity thereof was 90%,the air permeability in the thickness direction thereof was 0.9seconds/100 mL as represented by a Gurley air permeability, and thewater entry pressure (limit water entry pressure) thereof was 100 kPa.

[Sound-Transmitting Membrane C]

A non-porous PET film (LUMIRROR #5AF53, manufactured by TorayIndustries, Inc.) was prepared as the sound-transmitting membrane C. Thethickness of the sound-transmitting membrane C was 4 μm, the surfacedensity thereof was 5.5 g/m², the air permeability in the thicknessdirection thereof was 10,000 seconds/100 mL or more as presented as aGurley air permeability and the water entry pressure (limit water entrypressure) thereof was 650 kPa.

(Preparation of Support Layer)

In the present example, 12 types of waterproof sound-transmittingmembers (samples 1 to 12) were produced. For the respective samples, thefollowing support layers were prepared.

1. Mesh (1) Resin Mesh Having PET Skeleton Samples 1 and 12

#420 (thickness: 60 μm, surface density: 39.7 g/m², air permeability:500 cm³/(cm²-sec) or more, wire diameter: 33 μm, space ratio: 21%,opening: 27 μm), manufactured by NBC Meshtec Inc.

(2) Wire Mesh Having Stainless Skeleton Sample 2

MS-250 (thickness: 62 μm, surface density: 109.3 g/m², air permeability:500 cm³/(cm²-sec) or more, wire diameter: 30 μm, space ratio: 50%,opening: 72 μm), manufactured by ASADA MESH CO., LTD.

Sample 3

SHS-380 (thickness: 33 μm, surface density: 37.2 g/m², air permeability:500 cm/(cm²-sec) or more, wire diameter: 14 μm, space ratio: 62%,opening: 53 μm), manufactured by ASADA MESH CO., LTD.

Sample 4

BS-400 (thickness: 55 μm, surface density: 117.6 g/m², air permeability:370 cm³/(cm²-sec), wire diameter: 23 μm, space ratio: 41%, opening: 41μm), manufactured by ASADA MESH CO., LTD.

Sample 5

MS-640 (thickness: 35 μm, surface density: 78.2 g/m², air permeability:260 cm³/(cm²-sec), wire diameter: 15 μm, space ratio: 39%, opening: 25μm), manufactured by ASADA MESH CO., LTD.

Sample 6

MS-730 (thickness: 28 μm, surface density: 63.3 g/m², air permeability:260 cm³/(cm²-sec), wire diameter: 13 μm, space ratio: 40%, opening: 22μm), manufactured by ASADA MESH CO., LTD.

Sample 7 (Comparative Example)

#100 (thickness: 200 μm, surface density: 480.0 g/m², air permeability:500 cm³/(cm²-sec) or more, wire diameter: 80 μm, space ratio: 50%,opening: 175 μm), available from Eggs (TAIHO TRADING)

2. Through-Hole Sheet Sample 8

A through-hole sheet used for the support layer of sample 8 was preparedas follows.

A commercially available non-porous PET sheet (Track Etched Membrane,thickness: 45 μm, manufactured by it4ip) having a plurality of throughholes formed so as to penetrate the sheet in the thickness direction wasprepared. The through holes of the sheet had a diameter of 3.0 μm, andthe pore density of the sheet was 2.0×10⁶ holes/cm². Next, the preparedPET sheet was immersed for 30 minutes in an etching treatment solution(aqueous solution having a potassium hydroxide concentration of 20% bymass) kept at 80° C. After the end of etching, the sheet was taken outfrom the treatment solution, immersed in RO water (reverse osmosismembrane filtered water) for cleaning, and then dried in a drying ovenat 50° C. to obtain a non-porous resin sheet having a plurality ofthrough holes formed so as to penetrate the sheet in the thicknessdirection. The through hole diameter of the obtained resin sheet was 5.9μm, and the area of a cross-section perpendicular to a direction alongthe central axis of each through hole was constant in the thicknessdirection of the sheet. The pore density was the same before and afterthe etching. Next, the produced sheet was dipped in a liquid repellenttreatment solution for 3 seconds and left to dry at room temperature for30 minutes to form a liquid repellent layer on the surface of the sheetand the inner peripheral surfaces of the through holes, therebyobtaining a through-hole sheet. A solution (liquid repellent agentconcentration: 1.0% by mass) obtained by diluting a liquid repellentagent (X-70-029C, manufactured by Shin-Etsu Chemical Co., Ltd.) with adiluent (FS thinner, manufactured by Shin-Etsu Chemical Co., Ltd.) wasused as the liquid repellent treatment solution.

The thickness of the obtained through-hole sheet was 45 μm, the surfacedensity thereof was 27.7 g/m², the porosity thereof was 40%, the airpermeability thereof was 15.5 cm³/(cm².sec), and the through holediameter thereof was 5.9 μm. The shape of a cross-section of eachthrough hole in the sheet was uniform from one main surface of the sheetto the other main surface of the sheet.

3. Nonwoven Fabric Sample 9

HOP15 (material: polyethylene, thickness: 63 μm, surface density: 15.2g/cm², air permeability: 500 cm³/(cm² sec) or more), manufactured byHirose Paper Mfg Co., Ltd.

Sample 10 (Comparative Example)

HOP60HCF (material: polyethylene, thickness: 170 μm, surface density:60.0 g/cm², air permeability: 46.0 cm³/(cm²-sec) or more), manufacturedby Hirose Paper Mfg Co., Ltd.

4. Resin Net Having Polypropylene Skeleton Sample 11 (ComparativeExample)

Conwed Net X06065 (thickness: 350 μm, surface density: 105.0 g/m², airpermeability: 500 cm³/(cm²-sec) or more, wire diameter: 200 μm, spaceratio: 50%, opening: 660 μm), available from SAN-AI OIL CO., LTD.

(Production of Waterproof Sound-Transmitting Member)

Samples 1 to 12 were produced as follows using the prepared waterproofsound-transmitting membranes and support layers. The sound-transmittingmembrane A was used for samples 1 to 11, and the sound-transmittingmembrane B was used for sample 12.

The prepared waterproof sound-transmitting membranes and support layerswere each cut into a circle having a diameter of 5.8 mm. Separately fromthis, a double-faced adhesive tape A (a ring shape with an outerdiameter of 5.8 mm and an inner diameter of 1.5 mm, thickness: 50 μm,No. 5605 manufactured by Nitto Denko Corporation) and a double-facedadhesive tape B (a ring shape with an outer diameter of 5.8 mm and aninner diameter of 1.5 mm, thickness: 50 μm, No. 5605 manufactured byNitto Denko Corporation) were prepared.

Next, the double-faced adhesive tape A was attached to one main surfaceof each waterproof sound-transmitting membrane, and the double-facedadhesive tape B was attached to the other main surface of eachwaterproof sound-transmitting membrane. The double-faced adhesive tapesA and B were attached to each waterproof sound-transmitting membranesuch that the outer circumferences of the tapes and the circumference ofthe waterproof sound-transmitting membrane coincided with each other.Next, the double-faced adhesive tape A on the one main surface and thesupport layer were attached together such that the double-faced adhesivetape A was interposed between the waterproof sound-transmitting membraneand the support layer. The support layer was attached such that theouter circumference of the double-faced adhesive tape A and thecircumference of the support layer coincided with each other. Next, afurther double-faced adhesive tape A was attached to the exposed surfaceof the support layer. The further double-faced adhesive tape A wasattached to the support layer such that the outer circumference of thetape and the circumference of the support layer coincided with eachother. Thus, samples 1 to 12 were produced, which are each a waterproofsound-transmitting member in which the area of the non-joining region is1.8 mm², and the spacing distance between the waterproofsound-transmitting membrane and the support layer in the non-joiningregion is 50 μm, and which has a fixing portion composed of adouble-faced adhesive tape, on each main surface. In each sample, theproportion of the area of the non-joining region to the sum of the areaof the joining region and the area of the non-joining region when viewedin the direction perpendicular to the main surface of the waterproofsound-transmitting membrane was 7%.

Next, methods for evaluating the waterproof sound-transmitting membranesand the support layers used for producing samples 1 to 12, and methodsfor evaluating produced samples 1 to 12 will be described.

[Thickness]

The thicknesses of the waterproof sound-transmitting membranes and thesupport layers were measured with a dial gauge.

[Surface Density]

The surface densities of the waterproof sound-transmitting membranes andthe support layers were each obtained by measuring the mass of thewaterproof sound-transmitting membrane or support layer punched out in acircle having a diameter of 48 mm and converting the measured mass intoa mass per 1 m² of the main surface area.

[Porosity]

The porosities of the sound-transmitting membranes were obtained by theabove-described method.

[Air Permeability]

The air permeability in the thickness direction of each waterproofsound-transmitting membrane was obtained as a Gurley air permeabilityaccording to Method B (Gurley method) of air permeability measurementspecified in JIS L1096. The air permeability in the thickness directionof each support layer having higher air permeability than the waterproofsound-transmitting membranes was obtained according to Method A (Fraziermethod) of air permeability measurement specified in JIS L1096.

[Water Entry Pressure]

The water entry pressure (limit water entry pressure) of each waterproofsound-transmitting membrane was measured according to Method A (lowwater pressure method) or Method B (high water pressure method) of thewater resistance test in JIS L1092 using the above-described measurementjig.

[Water Pressure Retention Test]

A water pressure retention test for the waterproof sound-transmittingmembranes and samples 1 to 12 was performed by the above-describedmethod. The conditions for the test were selected from the following ato c in accordance with the water entry pressure (limit water entrypressure) of each waterproof sound-transmitting membrane. Specifically,for the sound-transmitting membranes A and C having a water entrypressure of 650 kPa or more and samples 1 to 11 including thesound-transmitting membrane A, the water pressure retention test wasperformed under Condition a and Condition b. For the sound-transmittingmembrane B having a water entry pressure of 100 kPa and sample 12including the sound-transmitting membrane B, the water pressureretention test was performed under Condition c and Condition b. In thetest, the case where water leakage occurred at the waterproofsound-transmitting membrane was determined as bad (x), and the casewhere no water leakage occurred at the waterproof sound-transmittingmembrane was determined as good (∘).

Condition a: the water pressure was 500 kPa, and the water pressureapplication time was 10 minutes.

Condition b: the water pressure was 700 kPa, the water pressureapplication time was 30 minutes, and the test was repeated 30 times withthe interval between each test being set as 1 minute.

Condition c: the water pressure was 60 kPa, and the water pressureapplication time was 10 minutes.

[Insertion Loss]

Insertion losses (insertion loss at 200 Hz and insertion loss at 1 kHz)of the waterproof sound-transmitting membranes and samples 1 to 12 weremeasured before and after the water pressure retention test wasperformed. For samples 1 to 11 and the sound-transmitting membranes Aand C, insertion losses before and after the water pressure retentiontest under Condition a were measured. For sample 12 and thesound-transmitting membrane B, insertion losses before and after thewater pressure retention test under Condition c were measured. Theinsertion losses were measured by the following method using a dummyhousing simulating a housing of a mobile phone.

As shown in (a) and (b) of FIG. 8, a speaker unit 65 to be housed in thedummy housing was produced. Specifically, the speaker unit 65 wasproduced as follows. A speaker 61 (SCC-16A, manufactured by STARMICRONICS CO., LTD.), which is a sound source, and fillers 63A, 63B, and63C composed of a urethane sponge and used for housing the speaker 61and preventing unnecessary diffusion of sound from the speaker(preventing, as much as possible, generation of sound to be inputtedinto a microphone for evaluation without passing through a waterproofsound-transmitting membrane or waterproof sound-transmitting membersample to be evaluated), were prepared. A sound-transmitting port 64having a circular cross-section with a diameter of 5 mm is provided inthe filler 63A in the thickness direction thereof. A cut having a shapecorresponding to the shape of the speaker 61 and a cut used for housinga speaker cable 62 and guiding the speaker cable 62 to the outside ofthe speaker unit 65 are provided in the filler 63B. Next, the fillers63C and 63B were overlaid on each other, and the speaker 61 and thespeaker cable 62 were housed in the cuts of the filler 63B. Next, thefiller 63A was overlaid such that sound is transmitted from the speaker61 through the sound-transmitting port 64 to the outside of the speakerunit 65, to obtain the speaker unit 65 ((b) of FIG. 8).

Next, as shown in (c) of FIG. 8, the produced speaker unit 65 was housedinside a dummy housing 51 (made of polystyrene, outer shape: 60 mm×50mm×28 mm) simulating a housing of a mobile phone. Specifically, thespeaker unit 65 was housed as follows. The prepared dummy housing 51includes two portions 51A and 51B, and the portions 51A and 51B can befitted to each other. A sound-transmitting port 52 (having a circularcross-section with an inner diameter of 1 mm) through which soundemitted from the speaker unit 65 housed inside is transmitted to theoutside of the dummy housing 51 and a guide hole 53 for guiding thespeaker cable 62 to the outside of the dummy housing 51 are provided inthe portion 51A. By fitting the portions 61A and 51B to each other, aspace having no opening other than the sound-transmitting port 52 andthe guide hole 53 was formed inside the dummy housing 51. The producedspeaker unit 65 was placed on the portion 51B, and the portion 51A andthe portion 51B were then fitted to each other, thereby housing thespeaker unit 65 inside the dummy housing 51. At this time, thesound-transmitting port 64 of the speaker unit 65 and thesound-transmitting port 52 of the portion 51A were overlapped such thatsound is transmitted from the speaker 61 through both sound-transmittingports 64 and 52 to the outside of the dummy housing 51. The speakercable 62 was drawn from the guide hole 53 to the outside of the dummyhousing 51, and the guide hole 53 was closed with putty.

Next, as shown in (d) of FIG. 8, each sample 83 (area of non-joiningregion: 1.8 mm²) before or after the water pressure retention test wasfixed to the sound-transmitting port 52 of the dummy housing 51 by thefixing portion (double-faced adhesive tape A) at the waterproofsound-transmitting membrane side of the sample. The sample 83 was fixedsuch that the entirety of the non-joining region of the sample 83 waslocated in the opening of the sound-transmitting port 52 when viewed inthe direction perpendicular to the main surface of the waterproofsound-transmitting membrane.

Next, as shown in (e) of FIG. 8, a microphone 71 (SPU0410LR5H,manufactured by Knowles Acoustics) was fixed to the support layer sideof the sample 83 so as to cover the non-joining region of the sample 83.The microphone 71 was fixed by the fixing portion (further double-facedadhesive tape A) at the support layer side of the sample 83. Thedistance between the speaker 61 and the microphone 71 when themicrophone 71 is fixed varies by several hundred micrometers dependingon the thickness of the waterproof sound-transmitting member sample tobe evaluated, but was within the range of 23 to 24 mm. Next, the speaker61 and the microphone 71 were connected to an acoustic evaluationapparatus (Multi-analyzer System 3560-B-030, manufactured by Brueel &Kjaer Sound & Vibration Measurement A/S), a solid state response (SSR)mode (test signal: 20 Hz to 20 kHz, sweep up) was selected and executedas an evaluation method, and the insertion loss of the sample 83 wasevaluated. The insertion loss was automatically determined from a testsignal inputted from the acoustic evaluation apparatus to the speaker 61and a signal received by the microphone 71. Prior to evaluating theinsertion loss of the sample 83, a value (blank value) of insertion losswhen the sample 83 was removed had been determined in advance. The blankvalue was −24 dB at a frequency of 1 kHz. The insertion loss of thesample 83 is a value obtained by subtracting the blank value from avalue measured by the acoustic evaluation apparatus. As the value ofinsertion loss is lower, sound outputted from the speaker 61 ismaintained at a higher level (sound volume).

The insertion loss of each waterproof sound-transmitting membrane wasmeasured as follows. The waterproof sound-transmitting membrane, beforeor after the water pressure retention test, to be evaluated was cut outinto a circle having a diameter of 5.8 mm. The double-faced adhesivetape A was attached to each main surface of the cut-out waterproofsound-transmitting membrane. Each tape A was attached to the waterproofsound-transmitting membrane such that the outer circumference of thetape and the circumference of the waterproof sound-transmitting membranecoincided with each other. Next, the waterproof sound-transmittingmembrane was fixed to the sound-transmitting port 52 of the dummyhousing 51 by one of the tapes A. The waterproof sound-transmittingmembrane was fixed such that the entirety of the sound-transmissionregion (circular region with a diameter of 1.5 mm corresponding to theopening of the double-faced adhesive tape A) was located in the openingof the sound-transmitting port 52 when viewed in the directionperpendicular to the main surface of the membrane. Next, the microphone71 was fixed so as to cover the sound-transmission region of thewaterproof sound-transmitting membrane, and the insertion loss of thewaterproof sound-transmitting membrane was measured by theabove-described method. The microphone 71 was fixed to the waterproofsound-transmitting membrane by the other tape A.

[Sound Transmission Characteristics Decrease Rate]

The sound transmission characteristics decrease rates of the waterproofsound-transmitting membranes and samples 1 to 12 were determined by theequation: sound transmission characteristics decrease rate(%)=(L2−L1)/L1×100 from the insertion loss (insertion loss at 1 kHz) L1before the water pressure retention test and the insertion loss(insertion loss at 1 kHz) L2 after the water pressure retention test.

[Degree of Change in Air-Permeability Characteristics]

For each of the sound-transmitting membrane A and samples 1 to 6including the sound-transmitting membrane A, an air permeability (airpermeability in the direction of permeation through thesound-transmitting membrane A or through the sound-transmitting membraneA and the support layer) was measured before and after the waterpressure retention test was performed, and the degree of change inair-permeability characteristics of the sample before and after thewater pressure retention test was evaluated. The degree of change inair-permeability characteristics was determined by the formula:|(AP2−AP1)|/AP1×100(%), where the air permeability of each of thesound-transmitting membrane A and the samples before the water pressureretention test was A1 and the air permeability of each of thesound-transmitting membrane A and the samples after the water pressureretention test was A2. The air permeability of each of thesound-transmitting membrane A and the samples was obtained as an airresistance t_(K) with a pressure sensor type air permeability tester(EG02-S, manufactured by Asahi Seiko Co., Ltd.) capable of performingthe Oken type testing machine method specified in JIS P8117: 2009, usingthe above-described measurement jig (a polycarbonate disc having athickness of 2 mm and a diameter of 47 mm and having a through hole witha diameter of 1 mm). In addition, air permeability measurement after thewater pressure retention test was performed after the sound-transmittingmembrane or the sample was dried at 60° C. for 1 hour after the test.

Each table below shows the evaluation results for the sound-transmittingmembranes A to C and samples 1 to 12.

TABLE 1 Sample No. 1 2 3 4 5 6 Sound-transmitting membrane A Mesh PETSupport layer skeleton Stainless skeleton Thickness [μm] 60 62 33 55 3528 Weight per unit area [g/m²] 39.7 109.3 37.2 117.6 78.2 63.3 Wirediameter [μm] 33 30 14 23 15 13 Space ratio [%] 21 50 62 41 39 40Opening [μm] 27 72 53 41 25 22 Air permeability [cm³/(cm²/sec)] 500 or500 or 500 or 370 260 260 (Frazier) more more more Water pressureretention test 500 kPa × 10 min ○ ○ ○ ○ ○ ○ 700 kPa × 30 min ○ ○ ○ ○ ○ ○×30 cycles Sound transmission characteristics 200 Hz 8.8 9.2 7.9 8.8 8.67.6 before water pressure retention test  1 kHz 6.2 6.7 6.0 6.7 6.5 5.9Sound transmission characteristics 200 Hz 1.4 1.8 0.5 1.4 1.2 0.2 beforewater pressure retention test  1 kHz 0.8 1.3 0.6 1.3 1.1 0.5 (incrementwith respect to sound- transmitting membrane alone) Sound transmissioncharacteristics 200 Hz 8.6 8.9 8.0 8.4 8.2 7.8 after water pressureretention test  1 kHz 6.3 6.8 6.3 6.8 6.5 6.1 Sound transmissioncharacteristics [%] 1.0 0.8 4.6 1.7 0.1 3.1 decrease rate (1 kHz) Degreeof change in air- [%] 2 3 1 3 1 3 permeability characteristics

TABLE 21 Sample No. 7 10 11 (Com. (Com. (Com. Example) 8 9 Example)Example) 12 Sound-transmitting membrane A B Mesh Through- Mesh Stainlesshole PET Support layer skeleton sheet Nonwoven fabric Net skeletonThickness [μm] 200 45 63 170 350 60 Weight per unit area [g/m²] 480 27.715.2 60.0 105.0 39.7 Wire diameter [μm] 80 — — — 200 33 Space ratio(porosity) [%] 50 40 — — 50 21 Opening [μm] 175 — — — 660 27 Airpermeability [cm³/(cm²/sec)] 500 or 15.5 500 or 46.0 500 or 500 or(Frazier) more more more more Water pressure retention test 500 kPa × 10min ○ ○ ○ ○ ○ —  60 kPa × 10 min — — — — — ○ 700 kPa × 30 min ○ ○ ○ ○ ○x ×30 cycles Sound transmission characteristics 200 Hz 22.6 11.3 13.419.9 41.1 1.2 before water pressure retention test  1 kHz 12.3 85 9.811.5 26.5 2.4 Sound transmission characteristics 200 Hz 15.2 3.9 6.012.5 33.7 −0.1 before water pressure retention test  1 kHz 6.9 3.1 4.46.1 21.1 −0.1 (increment with respect to sound- transmitting membranealone) Sound transmission characteristics 200 Hz 24.3 13.6 19.2 21.343.9 1.5 after water pressure retention test  1 kHz 13.5 9.0 10.3 12.331.5 2.5 Sound transmission characteristics [%] 9.8 5.9 5.1 6.6 18.9 4.2decrease rate (1 kHz)

TABLE 3 (Evaluation of sound-transmitting membrane alone: No supportlayer) Sound-transmitting membrane A B C Thickness [μm] 10 4 4 Weightper unit area [g/m²] 14.5 5.0 5.5 Porosity [%] 30 90 0 Air permeability(Gurley) [seconds/100 100 0.9 10000 mL] or more Water pressure retention500 kPa × 10 min ∘ — ∘ test 60 kPa × 10 min — ∘ — 700 kPa × 30 x x x min× 30 cycles Sound transmission 200 Hz 7.4 1.3 5.9 characteristics beforewater 1 kHz 5.4 2.5 5.3 pressure retention test Sound transmission 200Hz 8.5 1.9 39.1 characteristics after water 1 kHz 6.7 3.0 30.0 pressureretention test Sound transmission [%] 24.1 20.0 466.0 characteristicsdecrease rate (1 kHz) Degree of change in air- [%] 7 — — permeabilitycharacteristics

As shown in Tables 1 to 3, in samples 1 to 6, 8, 9, and 12 including asupport layer having a thickness less than 100 m, high soundtransmission characteristics (low insertion loss) were achieved. Inaddition, low values were obtained for not only insertion loss for soundof 1 kHz but also insertion loss for sound of 200 Hz. Furthermore, insamples 1 to 6, 8, 9 and 12, low insertion loss was achieved even thoughthe area of the non-joining region was 1.8 mm² and very small. Amongthese samples, particularly low insertion loss was achieved in samples 1to 6 in which the support layer is a mesh. In addition, in samples 1 to6, the sound transmission characteristics decrease rate was particularlyreduced.

Moreover, among samples 1 to 6, 8, 9, and 12, in samples 1 to 6, 8, and9 in which the sound-transmitting membrane A, which is a microporousPTFE membrane, was used as the waterproof sound-transmitting membrane,very high waterproofness was achieved, that is, no water leakageoccurred at the waterproof sound-transmitting membrane even when thewater pressure retention test was repeated 30 times under the conditionsof a water pressure of 700 kPa and a water pressure application time of30 minutes.

INDUSTRIAL APPLICABILITY

The technology of the present invention can be applied to variouselectronic devices including: wearable devices such as a smart watch;various cameras; communication devices such as a mobile phone and asmartphone; and sensor devices.

DESCRIPTION OF THE REFERENCE CHARACTERS

-   -   1 waterproof sound-transmitting member    -   2 waterproof sound-transmitting membrane    -   3 support layer    -   4 non-joining region    -   5 joining region    -   6 joining portion    -   7A, 7B fixing portion    -   8 opening    -   11 base film    -   12 separator    -   20 smartphone    -   22 housing    -   23, 24 opening    -   51 dummy housing    -   51A, 51B portion (of dummy housing 51)    -   52 sound-transmitting port    -   53 guide hole    -   61 speaker    -   62 speaker cable    -   63A 63B, 63C filler    -   64 sound-transmitting port    -   65 speaker unit    -   71 microphone    -   83 sample

1. A waterproof member comprising a waterproof membrane configured toprevent entry of water while permitting sound and/or gas to passtherethrough, and a support layer having air permeability in a thicknessdirection thereof, wherein the member has a joining region where thewaterproof membrane and the support layer are joined, and a non-joiningregion where the waterproof membrane and the support layer are spacedapart from each other, the non-joining region is surrounded by thejoining region when viewed in a direction perpendicular to a mainsurface of the waterproof membrane, and a thickness of the support layerin the non-joining region is less than 100 μm.
 2. The waterproof memberaccording to claim 1, wherein the support layer is a nonwoven fabric, awoven fabric, a net, a mesh, or a through-hole sheet.
 3. The waterproofmember according to claim 1, wherein the support layer is a mesh.
 4. Thewaterproof member according to claim 1, wherein an area of thenon-joining region when viewed in the perpendicular direction is 12 mm²or less.
 5. The waterproof member according to claim 1, wherein aproportion of the area of the non-joining region to a sum of an area ofthe joining region and the area of the non-joining region when viewed inthe perpendicular direction is 20% or less.
 6. The waterproof memberaccording to claim 1, wherein the waterproof membrane includes apolytetrafluoroethylene (PTFE) membrane.
 7. The waterproof memberaccording to claim 1, wherein air permeability in a thickness directionof the waterproof membrane is 20 seconds/100 mL or more as representedby a Gurley air permeability.
 8. The waterproof member according toclaim 1, wherein the waterproof membrane and the support layer arejoined by a double-faced adhesive tape in the joining region.
 9. Thewaterproof member according to claim 1, wherein a spacing distancebetween the waterproof membrane and the support layer in the non-joiningregion is 200 μm or less.
 10. The waterproof member according to claim1, wherein a fixing portion having a shape surrounding the non-joiningregion when viewed in the direction perpendicular to the main surface ofthe waterproof membrane is formed on a surface, of the waterproofmembrane, opposite to a surface, of the waterproof membrane, joined tothe support layer and/or on a surface, of the support layer, opposite toa surface, of the support layer, joined to the waterproof membrane. 11.An electronic device comprising: a housing having an opening; and thewaterproof member according to claim 1 attached to the housing so as toclose the opening, wherein the member is attached to the housing suchthat the waterproof membrane side of the member faces the outside of thehousing and the support layer side of the member faces the inside of thehousing.
 12. The electronic device according to claim 11, wherein asound conversion part configured to perform conversion between anelectric signal and sound is housed in the housing, and the opening islocated between the sound conversion part and the outside of thehousing.